Compositions and methods for preferential distribution of active agents to injury sites

ABSTRACT

Compositions are provided for preferential distribution of active agents to injury sites. Such compositions may comprise a ligand with hydrophilic properties and one or more active agents, such as compounds comprising hydrophilic metal ions. Because the delivery ligand and the active agent are specifically selected so the interactions between them are mainly of an ionic nature so that binding of the active agent to the delivery ligand and release of the active agent into the target site are not dependent on enzymatic activity. Methods of using such compositions are also disclosed.

FIELD OF THE INVENTION

This invention relates to methods and compositions for targeted drugdelivery.

BACKGROUND OF THE INVENTION

Targeted delivery of therapeutic agents to specific organs is a highlychallenging, exponentially developing area of experimental andtranslational biomedicine. In traditional drug delivery system, after apatient is administered a therapeutic agent, the agent is distributedthroughout the patients' body via the systemic blood circulation.Because only a small amount of the therapeutic agent can reach the organon which it needs to act, a high initial dose of the therapeutic agentneeds to be administered to the patient. Administering a high dose oftherapeutic agent to a patient is likely to increase the systemicconcentration of the therapeutic agent, which may have an adverse effecton the patient's healthy organs. If targeted delivery is successful, itwould result in a significant reduction in drug toxicity, reduction ofthe drug dose, and increased treatment efficacy.

Accordingly, there is a need in the art for compositions and methodsthat enable targeted delivery of therapeutic agents to specific organs.

SUMMARY OF THE INVENTION

One aspect of the invention provides compositions for preferentialdistribution of one or more active agents to an injury site. Suchcompositions may comprise a delivery ligand and at least one activeagent, preferably a metal ion, capable of forming ionic bonds with thedelivery ligand.

In various embodiments, the composition comprises between about 10 andabout 60% weight per volume of the delivery ligand, which may beselected from ligands with hydrophilic properties.

The active agent can comprise a metal ion capable of forming ionic bondswith the delivery ligand through electrostatic attraction to chelationsites, i.e. certain heteroatoms of the delivery ligand, for example, N,O, and S atoms, of the delivery ligand. The type of ionic bond can varyincluding electron sharing between one or more metal molecule and one ormore subunit present on one or more ligand molecules. In someembodiments, the active agent comprises a magnesium ion present inconcentration of about 0.1 to about 20% weight per volume.

The concentration of the delivery ligand in the instant compositionsdepends on the number of chelation sites. Since the delivery ligands arecomposed of repetitions of one or more sub-units (monomers), the numberof chelation sites is proportional to the molecular weight of theligand, with higher concentrations necessary for lower molecular weightligands to achieve preferential distribution of the active agent to theinjured site. One suitable delivery ligand comprises polyethylene glycol(PEG).

Another aspect provides methods of preferential distribution of one ormore active agents to an injury site. The methods comprise identifying apatient having an organ affected by a biological condition known tocause vessels supplying the organ to leak, and administering to thepatient a therapeutically effective amount of composition as describedabove.

Yet another aspect provides methods of treating organs affected by oneor more biological conditions known to cause vessels supplying the organto leak by preferentially distributing one or more active agent(s) knownto treat the one or more biological conditions. Such methods compriseidentifying a patient having such an organ and administering, preferablyparenterally, to the patient a therapeutically effective amount ofcomposition as described above.

The therapeutically effective amount can be calculated based on theweight of the patient. Generally, a patient needs to receive a dose ofat least about 0.5 to about 10 ml of composition per kg of patient'sweight. In the instant methods, at least one dose can be administeredwithin two half-lives of the delivery ligand. In some embodiments, atleast one dose can be administered within one half-life of the deliveryligand.

Additional features and advantages of various embodiments will be setforth in part in the description that follows, and in part will beapparent from the description, or may be learned by practice of variousembodiments. The objectives and other advantages of various embodimentswill be realized and attained by means of the elements and combinationsparticularly pointed out in the description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In part, other aspects, features, benefits and advantages of theembodiments will be apparent with regard to the following description,appended claims and accompanying drawings where:

FIG. 1 presents a graph comparing preferential distribution of PEG inthe injured site of the central nervous system tissue relative to anon-injured site following parenteral administration of a magnesium inPEG formulation initiated a few hours after injury.

FIG. 2 presents a graph showing preferential distribution of magnesiuminto the cerebrospinal fluid (CSF) following parenteral administrationof magnesium in a PEG formulation relative to a magnesium in salineformulation initiated a few hours after injury.

FIG. 3 presents a graph comparing CSF level of magnesium followingparenteral administration of magnesium in formulations containingvarious concentrations of PEG.

FIG. 4 presents a graph comparing CSF level of magnesium followingparenteral administration of magnesium in formulations containing PEGsof various molecular weights.

FIG. 5 presents a graph comparing CSF level of magnesium followingparenteral administration of a magnesium in PEG solution delivered atvarious speeds.

FIG. 6 presents a graph showing serum levels of magnesium followingparenteral administration of magnesium in a saline or a PEG formulationinitiated a few hours after injury.

FIG. 7 presents a graph showing PEG plasma levels followingadministration of a magnesium in PEG formulation initiated a few hoursafter injury.

FIG. 8 presents a graph showing PEG systemic exposure and half-lifefollowing administration of a magnesium in PEG formulation.

It is to be understood that the figures are not drawn to scale. Further,the relation between objects in a figure may not be to scale, and may infact have a reverse relationship as to size. The figures are intended tobring understanding and clarity to the structure of each object shown,and thus, some features may be exaggerated in order to illustrate aspecific feature of a structure.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities of ingredients,percentages or proportions of materials, reaction conditions, and othernumerical values used in the specification and claims, are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all subranges subsumedtherein. For example, a range of “1 to 10” includes any and allsubranges between (and including) the minimum value of 1 and the maximumvalue of 10, that is, any and all subranges having a minimum value ofequal to or greater than 1 and a maximum value of equal to or less than10, e.g., 5.5 to 10.

It is noted that, as used in this specification and the appended claims,the singular forms “a,” “an,” and “the,” include plural referents unlessexpressly and unequivocally limited to one referent.

One aspect of the invention provides compositions for preferentialdistribution of active agents to an injury site. The term “injury site,”as used herein, refers to an organ affected by a biological conditionknown to cause vessels supplying the organ to leak. Leaky blood vesselsallow for abnormal entrance into or escape from the vessels of fluidsubstances, such as blood and protein rich exudates. Biologicalconditions known to cause leaks in the vessels include, but are notlimited, to conditions that cause swelling such as acute inflammationthat can be observed from a few hours to a few weeks after acute tissueor bone injuries or chronic inflammation that can evolve over years whenassociated with degenerative disease such as age-related maculardegeneration and diabetic retinopathy or conditions that causeangiogenesis, such as cancer.

The instant compositions comprise a delivery ligand and at least oneactive agent where the interaction between the delivery ligand and theat least one active agent is mainly of an ionic nature. Theseinteractions could be defined as a “chelation” like effect. Cations ofthe active agent may form electrostatic attraction to certainheteroatoms of the delivery ligand, for example, N, O, and S atoms, ofthe delivery ligand. Such binding sites are referred herein as chelationsites. For example, although the hydrophilic polymer PEG as a whole isnon-ionic, the lone pairs of the electrons on the ether oxygens on thePEG chains imparts an anionic character to the polymer and can bind to ametal ion such as magnesium chloride through cations like Mg²⁺ or MgCl⁺.In one embodiment, the delivery ligand and the active agent arespecifically selected so the interactions between them are mainly of anionic nature so that the binding of the active agent of the deliveryligand and release of the active agent into the target site are notdependent on enzymatic activity.

Delivery ligands for the instant compositions may meet the followingcriteria: 1) they are water soluble; 2) they are rapidly cleared fromthe intact blood vessels and excreted; 3) they accumulate preferentiallywhere the blood vessels leak; 4) they possess hydrophilic properties;and 5) they possess chelation sites suitable for ionic binding withcations.

As noted above, the delivery ligands may be rapidly excreted from thebody when the blood vessels are intact. Accordingly, delivery ligandscan have a half-life less than 3 hours, less than 2 hours or less than 1hour. The rate of systemic clearance or half-life and excretion of adelivery ligand is related to the molecular weight of the ligand, withhigher molecular weight ligands having longer half-lives. Furthermore,for the same molecular weight, hydrophilic ligands have shorterhalf-lives than more hydrophobic ligands. Hydrophilic ligands that canbe excreted mostly unchanged through urine have shorter half-life thanligands that requires some transformation before excretion. For example,since 24,000 Da is the cut-off for glomerular filtration, any ligandheavier than 24,000 DA needs to be degraded to some extent before it canbe excreted, which adds to its half-life. Accordingly, delivery ligandsmay be preferably selected from polymers with hydrophilic propertieshaving a molecular weight of less than about 24,000 DA.

The delivery ligand may be selected from a hydrophilic or an amphipathicpolymer. The term “hydrophilic polymer,” as used herein, means anymacromolecule (molecular weights of 200 daltons and greater) whichexhibits an affinity for or attraction to water molecules and whichcomprises multiple instances of an identical subunit (“monomer”)connected to each other in chained and/or branched structures. Thehydrophilic polymer component may be a synthetic or naturally occurringhydrophilic polymer.

Naturally occurring hydrophilic compounds include, but are not limitedto: proteins such as collagen and derivatives thereof, fibronectin,albumins, globulins, fibrinogen, and fibrin; carboxylatedpolysaccharides such as polymannuronic acid and polygalacturonic acid;aminated polysaccharides, particularly the glycosaminoglycans, e.g.,hyaluronic acid, chitin, chondroitin sulfate A, B, or C, keratinsulfate, keratosulfate and heparin; methyl cellulose, sodiumcarboxylmethyl cellulose and activated polysaccharides such as dextranand starch derivatives.

Useful synthetic hydrophilic compounds include, but are not limited to:polyalkylene oxides, particularly polyethylene glycol and poly(ethyleneoxide)-poly(propylene oxide) copolymers, including block and randomcopolymers; polyols such as glycerol, polyglycerol (particularly highlybranched polyglycerol), poly(polyethylene glycol methacryalte),poly(glycerol methacrylate), poly(glycerol acrylatete),poly(polyethylene glycol acrylate), poly(alkyl oxazoline), phosphorylcholine polymers, sodium and potassium polymethacrylate, sodium andpotassium polyacrylate, polymethacrylatic acid and polyacrylic acid,propylene glycol and trimethylene glycol substituted with one or morepolyalkylene oxides, e.g., mono-, di- and tri-polyoxyethylated glycerol,mono- and di-polyoxyethylated propylene glycol, and mono- anddi-polyoxyethylated trimethylene glycol; polyoxyethylated sorbitol,polyoxyethylated glucose; acrylic acid polymers and analogs andcopolymers thereof, such as polyacrylic acid per se, polymethacrylicacid, poly(hydroxyethyl-methacrylate), poly(hydroxyethylacrylate),poly(methylalkylsulfoxide methacrylate), poly(methylalkylsulfoxideacrylate) and copolymers of any of the foregoing, and/or with additionalacrylate species such as aminoethyl acrylate and mono-2-(acryloxy)-ethylsuccinate; polymaleic acid; poly(acrylamides) such as polyacrylamide perse, poly(methacrylamide), poly(dimethylacrylamide), andpoly(N-isopropyl-acrylamide); poly(olefinic alcohol)s such as poly(vinylalcohol); poly(N-vinyl lactams) such as poly(vinyl pyrrolidone),poly(N-vinyl caprolactam), and copolymers thereof; polyoxazolines,including poly(methyloxazoline) and poly(ethyloxazoline); andpolyvinylamines.

The term “amphipathic polymer,” as used herein, refers to anymacromolecule (molecular weights of 200 daltons and greater) which havelocalized quantum variations in charge giving rise to polarsubstructures and non-polar substructures. The polar substructuresevidence an affinity for or attraction to other polar molecularstructures such as water molecules (hydrophilic), while the nonpolarsubstructures exhibit an affinity or attraction for nonpolar moleculessuch as lipids, oils, greases, fats, etc. (lipophilic). Suitableamphipathic polymers include, but are not limited to, poloxamer P-188,polyetherester copolymers such as polyethylene glycol and polylbutyleneterephthalate copolymers, polyethylene glycol and polypropylencoxidecopolymers, polyethylene glycol and polypropylene glycol blockcopolymers.

Amphipathic polymers also include a family of polyetheramines known asJeffamine®. These polyetheramines contain primary amino groups attachedto the end of a polyesther backbone, which is typically based onpropylene oxide (PO), ethylene oxide (EO), or a mixture thereof. TheJeffamine® family includes monamines, diamines, triamines and secondaryamines. Jeffamine® may be procured from Huntsman Corporation,headquartered in The Woodlands, Tex.

In general, the concentration of the delivery ligand in the instantcompositions range between about 10 and 60% weight per volume, i.e., 10and 60 gm of ligand to 100 ml solution, between about 20 and about 40%weight per volume, or between about 30% and about 40% weight per volume.The concentration of the delivery ligand in the instant compositionsdepends on the number of chelation sites in the delivery ligand. Thedelivery ligands are composed of repeating sub-units of one or moretypes, at least some of which include chelation sites. Delivery ligandswith higher molecular weight are composed of a higher number ofsub-units, and thus they are more likely to have a higher number ofchelation sites than delivery ligands with lower molecular weight.Accordingly, as a general rule, the concentration of the delivery ligandwith higher molecular weight in the composition may be lower than theconcentration of the delivery ligand comprising the same sub-units andhaving a lower molecular weight. For example, when utilizing a deliveryligand with a molecular of 3350 DA, the composition preferably comprisesat least 20% weight to volume of the delivery ligand. In anotherexample, when utilizing a delivery ligand with a molecular of 300 DA,the composition preferably comprises at least 30% weight to volume ofthe delivery ligand.

In various embodiments, the delivery ligand may comprise polyethyleneglycol (PEG). PEGs of molecular weights between about 100 and 20,000 DA,more preferably between about 300 to 9000 DA are suitable, and mostpreferably between about 2,000 DA and about 4,000 DA for use as deliveryligands in instant compositions. PEGs of different molecular weights maybe obtained from, for example, Sigma-Aldrich, St. Louis, Mo., USA.

The term “active agent,” as used herein, refers to a chemical element orcompound that alleviates signs or symptoms of the biological conditionaffecting the targeted organ and causing vessels to leak. In someembodiments, the chemical structure of the delivery ligand and theactive agent are selected so they can form a complex mainly based oninteractions of ionic nature. The concentration of the active agent inthe instant compositions may range between about 0.1% to about 20%weight per volume. In some embodiments, the concentration of the activeagent in the instant compositions may range between 0.8 and 20% weightper volume.

In some embodiments, the active agent may be selected from metal ions,including, but not limited to, monodentate metal ions, such as potassiumand lithium; bidentate metal ions, such as magnesium and calcium;transition metals, such as iron, zinc, and copper; more complex metalions, such as aluminum; and compounds comprising such metal ions. Suchmetal ions form complexes with delivery ligands by forming ionic bondsthrough electrostatic attraction to certain heteroatoms of the deliveryligand, such as Nitrogen, Oxygen or Sulfur atoms. The type of ionic bondcan vary including electron sharing between one or more metal ions andone or more subunits of the delivery ligand. The metal counterion mayalso participate in the formation of the complex with the deliveryligand.

In some embodiments, the instant compositions may also includehydrophilic disease-modifying agents, neurotransmitter, neuropeptidesand neuronal receptor modulators, anti-inflammatory and immunomodulatoragents, antioxidants, anti-apoptotic agents; nootropic and growthagents, modulators of lipid formation and transport, modulators of bloodflow and vessel formation, analgesics, steroidal anti-inflammatory drugssuch as corticosteroids, non-steroidal anti-inflammatory drugs such assalicylates, COX-2 inhibitors, TNFα inhibitors, opiates andmorphinomimetics, among others.

In one embodiment, the bioactive agent comprises a magnesium compound.The concentration of magnesium in the instant compositions may rangebetween about 0.1% to about 20% weight per volume, more preferablybetween about 0.1% to about 10% weight per volume. Most preferably theconcentration of magnesium in the instant compositions is between about0.4 and about 4% weight per volume and higher than the concentration ofmagnesium found in serum, buffer or electrolyte solutions which normallyvary between 0-10 mM. Various magnesium salts may provide a source forthe magnesium compounds. Suitable magnesium salts include, but are notlimited to, magnesium sulfate, magnesium carbonate, magnesium chloride,magnesium oxide, magnesium hydroxide or any combination thereof. Thesecompounds are readily available commercially from, for example, SigmaAldrich, St. Louis, Mo., USA.

In addition to the delivery ligand and the active agents, the instantcompositions may include one or more pharmaceutically acceptablecarriers. The instant compositions may include excipients such assolvents, binders, fillers, disintegrants, lubricants, suspendingagents, surfactants, viscosity increasing agents, buffering agents,antimicrobial agents, among others. Many different pharmaceuticallyacceptable carriers and excipients are known and disclosed, for example,in Remington's Pharmaceutical Sciences, Lippincott Williams & Wilkins;21 edition (May 1, 2005).

By way of non-limiting examples, compositions disclosed in U.S. patentapplication Ser. Nos. 11/418,153 and 11/418,152, incorporated herein byreference in their entireties, may be employed.

In some embodiments, the instant compositions are prepared forparenteral administration. Parenteral administration is generallycharacterized by a subcutaneous, intramuscular, or intravenousinjection. Instant compositions for parenteral administration may beprepared as liquid solutions or suspensions, solid forms suitable forsolution in liquid prior to injection.

Another aspect of the invention is directed to methods for preferentialdistribution of active agents to an injury site. Such methods compriseidentifying a patient having an organ affected by a biological conditionknown to cause vessels supplying the organ to leak and administering toa patient a therapeutically effective amount of instant composition.

Yet another aspect of the invention is directed to methods of treatingorgans affected by one or more biological conditions known to causevessels supplying the organ to leak by preferentially distributing oneor more active agent(s) known to treat the one or more biologicalconditions. Such method comprises identifying a patient whose havingsuch an affected organ and administering to the patient atherapeutically effective amount of instant composition.

The term “treating” or “treatment” refers to executing a protocol, whichmay include administering one or more drugs to a patient (human orotherwise), in an effort to alleviate signs or symptoms of the disease.Alleviation can occur prior to signs or symptoms of disease appearing,as well as after their appearance. Thus, “treating” or “treatment”includes “preventing” or “prevention” of the disease. In addition,“treating” or “treatment” does not require complete alleviation of signsor symptoms, does not require a cure, and specifically includesprotocols which have only a marginal effect on the patient.

The term “therapeutically effective amount” means a quantity of theactive agent which, when administered to a patient, is sufficient toresult in an improvement in patient's condition. The improvement doesnot mean a cure and may include only a marginal change in patient'scondition. It also includes an amount of the active agent that preventsthe condition or stops or delays its progression. Generally, atherapeutically effective amount of the instant composition may beestimated based on patient's weight. In certain embodiments, patientpreferably receives a dose of at least about 0.5 to about 20 ml ofcomposition per kg of patient's weight, more preferably between about0.5 and 10 ml and most preferably between about 1 and 8 ml ofcomposition per kg of patient's weight. In one embodiment, the patientneeds to a receive a dose of about 0.1 to about 3 g of delivery ligandand about 4 to about 80 mg of the active agent per kg of patient'sweight, and most preferably between about 0.3 to about 2.5 g of thedelivery ligand and about 8 to about 65 mg of the active agent per kg ofpatient's weight. Repeated doses may be administered if necessary. Insome specific non-limiting embodiments, the composition administered toa patient may comprise PEG 3350 and magnesium chloride hexahydrate inthe above listed amounts.

Any diagnosing method known and used in the art may be utilized toidentify an organ affected by a biological condition known to causevessels supplying the organ to leak. Suitable diagnosing methodsinclude, but are not limited to, blood tests, urine tests, tissueswelling, pain, functional or neurological evaluations or medicalimaging tests, such as X-ray, ultrasound, CAT scans or MRI.

As noted above, preferred delivery ligands are rapidly cleared from theintact blood vessels and excreted from the patient's body unless theyaccumulate at the site of leaky vessels. Because such ligands are likelyto have a short half life in the body, they need to be administered to apatient rapidly. More specifically, it is desirable to administer a doseof the instant composition to the patient within two half-lives, andmore preferably within one half-life, of the delivery compound. Forexample, in some PEGs having a molecular weight between 1000 and 6000 DAmay be utilized. The half-lives of such PEGs in humans is between about30 and about 90 minutes, and thus it is desirable to administer a doseof the instant composition comprising such PEGs within 180 minutes totake in account for individual variations and most preferably within 90minutes. In another example, PEG of MW 3350 has a half-life of 29-42minutes in rats and better preferential distribution is observed whenthe magnesium in the PEG 3350 solution is administered within a periodless than 60 minutes.

Having now generally described the invention, the same may be morereadily understood through the following reference to the followingexample, which is provided by way of illustration and is not intended tolimit the present invention unless specified.

EXAMPLE

Methods and Tests Pertaining to Data in FIGS. 1-7:

Female Sprague-Dawley rats (Harlan Sprague-Dawley, Indianapolis, Ind.),weighing 250-300 grams each were given free access to food and waterbefore the experiment. The animals were anesthetized with ketamine (80mg/kg) and xylazine (10 mg/kg). Brain temperatures were monitored usinga rectal thermometer. The animals' body temperature was maintained at37° C. by using a water-jacketed heating pad. Brain temperature wasmonitored for 1 hour prior to injury to 6 hours following injury and wasrecorded at 30-minute intervals.

The spinal cord injury model utilized in the studies is described indetail (Rabchevsky et al, 2002). Young adult female Sprague-Dawley ratsreceived a spinal cord contusion using the Precision Systems andInstrumentation, LLC (Fairfax Station, Va.) pneumatic impactor. Prior tosurgery, rats were assigned to different treatment groups based on arandomized block design so that on any given surgery day all treatmentgroups were included. The rats were anesthetized with ketamine (80mg/.kg) and xylazine (10 mg/kg) before laminectomy was performed at the10^(th) thoracic vertebra (T₁₀). The vertebral column was stabilizedwith angled clamps on the upper thoracic (T8) and lumber (T11) levelsand the impactor with a tip diameter of 2 mm was delivered atapproximately 150 kdynes onto the exposed, intact dura overlying thedorsal spinal cord. The impactor was immediately removed, the woundirrigated with saline and the muscle and skin openings sutured together.

Two hours following injury, saline, 0.8% magnesium in saline or 0.8%magnesium in a 20 or 30% PEG 300 Da or 3350 Da formulations wereadministered by intravenous infusion of 5 mL/kg over a 10 to 60 minuteperiod. The right jugular vein was cannulated with PE 50 tubing for ivadministration. The cannula was secured through the back of the neck andcapped between infusion periods. Animals were re-anesthetized forre-administration of compounds. The contents of the infusion vials wereblinded to the investigators performing both the infusions and theanalyses.

Methods and Tests Pertaining to Data in FIG. 8:

Systemic exposure and half-life of the PEG component was evaluatedfollowing daily intravenous administration of 10-20 ml/kg of 0.8%magnesium in 30% PEG3350 formulation delivered over 30 minutes in rats.

Methods and Tests Pertaining to Data in FIGS. 1-8:

At various time points after infusion, cerebrospinal fluid and/or bloodsamples and/or spinal cord tissue with and without the injury site werecollected. The blood samples were processed to serum for the magnesiumassay or to plasma for the PEG assay.

Serum and CSF samples were analyzed for magnesium concentrations by theClinical Pathology Department at WIL Research Laboratories, LLC, 1407George Road, Ashland, Ohio 44805. Serum and CSF samples were reactedwith xylidyl blue in an alkaline solution containingethyleneglycol-bis(2-aminoehtylether)-N,N,N′,N′-tetraacetic acid (EGTA)to form a purple chromophore. The formation of the chromophore (andconsequently a reduction of the xylidyl blue) is proportional to theconcentration of Mg²⁺, measured by the instrument as a decrease in thexylidyl blue absorbance (600 nm). A Hitachi 912 clinical chemistryanalyzer assay was used for the determination of magnesium in serum andCSF.

Tissue and plasma concentrations of PEG-3350 in rat plasma were measuredusing a validated high performance liquid chromatograpy tandem massspectrometry (HPLC/MS/MS) method in positive electrospray ionizationmode. The method for the determination of PEG-3350 used acetonitrile tode-proteinize 200 μL of plasma. Following centrifugation of the plasmaor tissue homogenate, the supernatant fraction from each sample wasconcentrated by evaporation and reconstituted with mobile phase A priorto analysis. The samples were analyzed with an HPLC/MS/MS assay using aThermo Hypersil ODS column. The peak areas of PEG-3350 and thetheoretical concentrations of calibration standards were fit to theln-quadratic function, excluding the origin.

Results:

(1) PEG accumulates preferentially at the site of injury followingparenteral administration.

Quantitative evaluation of PEG spinal tissue levels using HPLC/MS/MSassay also indicated that PEG accumulates preferentially at the site ofinjury with PEG tissue levels of 3198 ug/ml found at the site of injury30 min post-infusion relative to 1238 ug/ml at a non-injured site. ThePEG spine tissue levels rapidly decreased over time such as the 3 hourspost-infusion 1431 ug/ml was found at the site of injury and 519 ug/mlat a non-injured site. These results are presented in FIG. 1. However, acertain amount of PEG must have remained at the site of injury becausethe PEG levels increased with the number of infusions. At 3 hourspost-infusions, PEG tissue levels at the site of injury were 1431 ug/mland 3891 ug/ml after one infusion and five infusions, respectively.

(2) PEG increases magnesium accumulation in the CNS compartment in SCIrats.

Magnesium levels in the cerebrospinal fluid (CSF) of SCI rats followingintravenous administration of a magnesium in saline solution ormagnesium in PEG solution were evaluated using a colorimetric assay. Aspresented in FIG. 2, thirty minutes after infusion, magnesium CSF levelswere similar for both formulations and ranged from 0.29-0.34 mmol/L.However, three hours post-infusion, magnesium CSF levels were increasedby two folds in the magnesium in PEG group (0.58 mmol/L) relative to nochanges in the magnesium in saline group (0.28 mmol/L). Similarly to thePEG spinal tissue levels, the magnesium CSF levels increased with thenumber of magnesium in PEG infusions. At 3 hours post-infusions,magnesium CSF levels of 0.58 mmol/L after and 0.97 mmol/L were recordedafter one and five infusions, respectively. As presented in FIGS. 3-5,the concentration and MW of the PEG component as well as the rate ofdelivery can influence the magnesium CSF levels achieved followingintravenous administration of magnesium in PEG formulations.

(3) The PEG formulation does not affect the magnesium systemic clearance

Referring to FIG. 6, the formulation of magnesium in a PEG solution didnot alter the systemic distribution of magnesium relative to magnesiumin saline solution. Cmax levels were observed at the end of the infusion(t=0) and reached about 2.00 mmol/L following administration ofmagnesium in saline or magnesium in PEG solutions. Magnesium serumlevels decreased rapidly over time and were back to baseline levels ataround 1-2 hours post-infusion.

(4) PEG is rapidly cleared from the systemic circulation

Referring to FIG. 7, in injured animals, the Cmax value for the PEGplasma level was observed at the end of the infusion and levelsdecreased rapidly to baseline level at 30 minutes post-infusion.Similarly in non-injured rats (FIG. 8), the Cmax value for the PEGplasma level was observed at the end of the infusion, levels decreasedrapidly leading to half-lives that varied between 0.49-0.69 hours infemale and male rats. Daily repeated infusions over 7 days did notaffect the PEG systemic exposure and clearance profiles.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention which is defined by the following claims.

What is claimed is:
 1. A method of increasing magnesium at a site of aspinal cord injury in a patient, the method comprising administering tothe patient a composition comprising a delivery ligand comprisingpolyethylene glycol (PEG) having a molecular weight of between about 100DA and about 20,000 DA and the polyethylene glycol comprises at least30% weight per volume of the composition and the composition comprisesabout 0.4% to about 4% weight per volume of magnesium, and at least onedose of the composition is administered within one half-life of thedelivery ligand wherein the half-life of the ligand is between about 30and about 90 minutes.
 2. The method of claim 1, wherein the compositioncomprises about 0.1 to about 3 g of ligand per kg of patient's bodyweight.
 3. The method of claim 1, wherein the interaction between thedelivery ligand and the magnesium is an ionic interaction.
 4. The methodof claim 1, wherein the site of the spinal cord injury comprises a leakyblood vessel.
 5. The method of claim 1, wherein the polyethylene glycolcomprises a molecular weight of between about 300 DA and about 9000 DA.6. The method of claim 1, wherein the composition comprises about 8 toabout 65 mg of the magnesium per kg of patient's body weight.
 7. Themethod of claim 1, wherein the magnesium comprises magnesium sulfate,magnesium carbonate, magnesium chloride, magnesium hydroxide, magnesiumoxide or a combination thereof.
 8. A method of treating a spinal cordinjury by increasing magnesium to the spinal cord injury, the methodcomprising administering a composition comprising a delivery ligandcomprising polyethylene glycol (PEG) having a molecular weight ofbetween about 100 DA and about 20,000 DA and the polyethylene glycolcomprises between about 30% to about 60% weight per volume of thecomposition and the composition comprises about 0.4% to about 4% weightper volume of magnesium, and at least one dose of the composition isadministered within two half-lives of the delivery ligand wherein thehalf-life of the ligand is between about 30 and about 90 minutes.
 9. Themethod of claim 8, wherein the composition comprises about 0.1 to about3 g of ligand per kg of patient's body weight.
 10. The method of claim8, wherein the interaction between the delivery ligand and the magnesiumcomprises an ionic interaction.
 11. The method of claim 8, wherein thepolyethylene glycol has a molecular weight of between about 300 DA andabout 9000 DA.
 12. The method of claim 8, wherein the compositioncomprises about 8 to about 65 mg of the magnesium per kg of patient'sbody weight.
 13. The method of claim 8, wherein the magnesium comprisesmagnesium sulfate, magnesium carbonate, magnesium chloride, magnesiumhydroxide, magnesium oxide or a combination thereof.
 14. The method ofclaim 8, wherein the composition comprises about 30% of the deliveryligand.
 15. The method of claim 1, wherein the composition isadministered intravenously at a dose of about 0.5 ml to about 10 ml ofthe composition per kg of patient body weight.
 16. The method of claim1, wherein the polyethylene glycol comprises about 30% weight per volumeof the delivery ligand.
 17. The method of claim 1, wherein thepolyethylene glycol comprises about 40% weight per volume of thedelivery ligand.
 18. The method of claim 1, wherein the composition isadministered by subcutaneous, intramuscular, or intravenous injection.19. The method of claim 1, wherein the composition is administered byintravenous injection.
 20. The method of claim 1, wherein thepolyethylene glycol comprises about 30% to about 40% weight per volumeof the composition and the polyethylene glycol comprises a molecularweight of between about 300 DA and about 9000 DA.
 21. The method ofclaim 20, wherein the magnesium comprises magnesium chloride.
 22. Themethod of claim 8, wherein the composition comprises a first compositioncomprising polyethylene glycol and a second composition comprisingmagnesium, the first and second compositions being administeredseparately.
 23. The method of claim 8, wherein a single dose of thecomposition is administered within a period less than 60 minutes. 24.The method of claim 8, wherein the PEG comprises PEG 3350, whichcomprises 30% of the composition.
 25. The method of claim 8, wherein thePEG comprises PEG 3350, which comprises 30% of the composition and thecomposition comprises an antioxidant.
 26. The method of claim 8, whereinthe composition comprises an antioxidant.